7-Ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxycamptothecin has been hitherto prepared by condensation of 7-ethyl-10-hydroxycamptothecin of formula
with 1-chlorocarbonyl-4-piperidinopiperidine hydrochloride of formula
in pyridine at room temperature. This method has been described in the following documents: U.S. Pat. No. 4,604,463 (T. M. Kanagawa, S. Sawada, K. Nokata, E. Sugino, M. Mutai), issued on Aug. 5, 1986; S. Sawada, S. Okajima, R. Alyama, K. Nokata, T. Furuta, T. Yokokura, E. Sugino, K. Yamachuchi, T. Miyasaka, Chemical and Pharmaceutical Bulletin 1991. 39(6), 1446-1454; WO 96/31513 (K. E. Henegar. J. C. Sih), published on Oct. 10, 1996; U.S. Pat. No. 6,235,907 (K. E. Henegar, J. C. Sih), issued on May 22, 2001; U.S. Pat. No. 6,444,820 (K. E. Henegar. J. C. Sih), issued on Sep. 3, 2002.